Light interception and its relation to structural differences in three Australian rainforest canopies

Relative differences in the seasonality of light penetrating the canopies of three Australian rainforests were measured directly with a quantum meter and indirectly using hemispherical photographs. The mossy microphyll fern forest had higher incident light levels (100–200 μEinstein m−2 per s) and more sky visible (21.8%) at ground level than the simple (5–20 μEinstein m−2 per s with 11.2% skylight) and complex (5–10 μEinstein m−2 per s with 10.8% skylight) notophyll vine forests. There were no significant changes in amounts of sky visible through the canopy over time (10 months) for any canopy, despite the fact that leaf‐fall was a seasonal event. Profile diagrams were constructed at each site to illustrate the depth and stratification of the canopy, and the differences in these structural features were related to the variation in light attenuation. Ecological aspects of light interception through rainforest canopies are discussed, including tree branch growth patterns and leafing phenologies, and seedling regeneration on the forest floor.